The black-billed magpie (Pica hudsonia), also known as the American magpie, is a bird in the corvid family found in the western half of North America. It is black and white, with the wings and tail showing black areas and iridescent hints of blue and blue-green. It was formerly treated as a subspecies of Pica pica (Eurasian magpie), but was separated as a species in its own in 2000 based on genetic studies.
This species prefers generally open habitats with clumps of trees, but can also commonly be found in farmlands and suburban areas. Historically associated with bison herds, it now lands on the backs of cattle to glean ticks and insects from them. Black-billed magpies commonly follow large predators, such as wolves, to scavenge from their kills. The species also walks or hops on the ground, where it obtains food items such as beetles, grasshoppers, worms, and small rodents.
The black-billed magpie builds domed nests which are made up of twigs and are located near the top of trees, usually housing six to seven eggs. Incubation, by the female only, starts when the clutch is complete, and lasts 16–21 days. The nestling period is three to four weeks. Black-billed magpies in the wild have a lifespan of six to seven years.
Black-billed magpies have a long history with humans, being featured in stories told by Indigenous tribes of the Great Plains. Where persecuted it becomes very wary, but otherwise it is fairly tolerant of human presence. Due to their perceived negative impact on cattle and game birds, black-billed magpies were hunted as a pest during the 1900s, and their population suffered as a result. Today, they are considered a species of least concern by the IUCN, and they are commonly seen throughout their range.
Taxonomy and systematics
The black-billed magpie was originally described in 1823 as "Corvus Hudsonius, Hudson's Bay Magpie" by Joseph Sabine in his report of an expedition to the North American Arctic. In previous encounters with the bird prior to its formal description, it had been presumed to be of the same bird as the magpies from Europe; Sabine wrote of it:
Based on the black-billed magpie's strong similarity to the European magpies, but also with the slight differences in smaller size and longer tail and wing length that Sabine observed, it was later reclassified as a subspecies of the European bird; with the separation of the magpies as a genus of their own (rather than in the crow genus Corvus as Sabine had done), its scientific name was generally cited as Pica pica hudsonia by the late 19th century. The generic name Pica is the Latin word for magpie, and the specific name hudsonia is from the Hudson Bay, where it was first distinguished as distinct.
The word "magpie" comes from a combination of "Mag", a nickname for Margaret, and "pie", the Middle English word for the Eurasian magpie. The name Margaret was associated with chattiness in the early 15th century, and was applied to the magpie because its calls were thought to sound like a person chattering.
The American Ornithologists' Union (AOU) 1880 first checklist of American birds called it "American magpie", as did still the 1931 fourth edition, but in the 1957 fifth edition it was renamed to "black-billed magpie", without explanation but presumably as a distinguishing counterpoint to the related yellow-billed magpie. In this edition, the AOU applied the name "black-billed magpie" to the whole of Pica pica, though this name had no history of use in the species' main range in Europe.
The black-billed magpie was then widely considered conspecific with the Eurasian magpie until mtDNA studies showed a relatively high divergence between the two species. It was also shown that the black-billed magpie was more closely related to California's yellow-billed magpie (Pica nuttalli) than it was to Eurasian magpies. Black-billed magpies are also shown to have different social behaviour and vocalizations from the Eurasian magpie, further indicating separate species. In 2000, the AOU accepted the black-billed magpie as a separate species Pica hudsonia.
Fossil evidence suggests that the ancestral North American magpie arrived in its current range around the mid-Pliocene, approximately 3–4 mya, having crossed the Bering land bridge. From there, the Eurasian and North American populations began to differentiate. The yellow-billed magpie lineage likely split off soon after due to the Sierra Nevada uplift and the beginning of an ice age. A comparatively low genetic difference, however, suggests that some gene flow between the black-billed and yellow-billed magpies still occurred during interglacial periods until the Pleistocene.
Description
The black-billed magpie is an unmistakable bird within its range. It is a medium-sized bird that measures from tip to tail. It is largely black, with white scapulars, belly, and primaries, and the wings and tail are an iridescent blue-green. The tail is made up of long, layered feathers, the middle pair of which extend further than the rest. The beak is uniformly black, oblong, and weakly curved toward the tip. Adults also have black irises.
Unlike most other members of the family Corvidae, the black-billed magpie is dimorphic in size and weight, though there can be overlap between the sexes. Males are, on average, 6–9% larger and 16–24% heavier than females, at , an individual wing chord of , and tail lengths of . Females weigh between , have individual wing chords of , and tail lengths of .
Juveniles have less iridescence on their wings and tail, buffier scapulars and belly, and they lack the distinctive long tail feathers. Their rectrices are typically rounder and narrower, and have more black on their wing-tips compared to mature adults. They also have pink mouth-linings and grey irises. All juvenile features will typically be gone by the first year's moult.
The black-billed magpie can be distinguished from the similar yellow-billed magpie by its longer tail and by the colour of the beak. They are on average slightly larger but with much overlap, long to the of yellow-billed magpie. Eurasian magpies are visually very similar to black-billed magpies; however, Eurasian magpies are slightly larger-bodied but have shorter tails and wings. They can also be distinguished based on their different vocalizations, as well as by their non-overlapping ranges.
Vocalizations
The vocalizations of the black-billed magpie consist of a number of calls variously described as tweets, coos, purrs, shrills and squawks, but the most common is an alarm call, called a chatter, that is described as a ka-ka-ka-ka, sometimes preceded with a skah-skah. This call is very different from that of the Eurasian magpie, but is similar to that of the yellow-billed magpie. At least one black-billed magpie, living with humans, has learned to imitate human speech.
Distribution and habitat Black-billed magpies are generally non-migratory, however some winter movement does occur. While the exact reason for these movements is unknown, it is thought to be a result of postbreeding dispersal and a subsequent return to their nesting sites. This species ranges from coastal southern Alaska, southwest Yukon Territory, central British Columbia, Alberta, Saskatchewan, Manitoba, and northwestern Ontario in the north, through the Rocky Mountains down south to all the Rocky Mountain states including New Mexico, Colorado, Utah, Wyoming, Idaho, and some bordering states as well. The range can extend as far east as northern Minnesota and Iowa, with casual records in northern Wisconsin and upper Michigan, but is thought to be limited further east and south by high temperature and humidity. The species is absent in California west of the Cascades and Sierra Nevada ranges, where it is replaced by the yellow-billed magpie.
During the breeding season the preferred habitat is riparian areas with thickets. The predilection for open habitats with clumps of trees means that the species lives in meadows and suburbs. Outside the breeding season, magpies can be found in their breeding habitat but also near feedlots, grain elevators, landfills, and around barns and houses.
Behaviour Breeding and nesting
Adult black-billed magpie typically form pairs which last year-round and often for life, in which case the remaining magpie may find another mate. "Divorces" are possible; one South Dakota study found low rates of divorce (8%) but one study in Alberta found that pairs had a 63% divorce rate over a 7-year period.
Black-billed magpies nest individually, and often situate their nests near the top of trees. Only the nest tree and its immediate surroundings are defended, and so it is possible for nests to be somewhat clumped in a location. When this happens (usually in areas with a limited number of trees or with abundant food resources), a diffuse colony is formed. In this, the black-billed magpie is intermediate between the Eurasian magpie, whose nests are much more spread out because a large territory is defended around each nest, and the yellow-billed magpie, which is always loosely colonial.
Nests are loose but large accumulations of branches, twigs, grass, rootlets, mud, fur, and other materials. Branches and twigs constitute the base and framework, while mud is used as anchor and in the nest cup. The cup is lined with materials found nearby, often grass, rootlets, and other soft material. A hood or dome is present on almost all nests, and if formed of twigs and branches that are loosely assembled. The nest will usually have a single side entrance. Nests are built by both sexes over 40–50 days, starting in February (though later in northern parts of the range). Nests have been shown to be quite durable, and occasionally old nests are repaired and reused across multiple breeding seasons.
If regularly disturbed, black-billed magpie pairs will aggressively defend their nest. If the disturbances continue, they will eventually either move the eggs or abandon the clutch altogether. Biologists who have climbed nest trees to measure magpie eggs have reported that the parents recognized them personally on subsequent days and started to mob them, overlooking other people in the vicinity.
Black-billed magpies generally start breeding in late March, with the breeding season ending in early July. While they typically only nest once per year, a second nesting may take place if the initial nesting fails early. The average clutch size is six or seven eggs, however females may lay up to thirteen eggs. The eggs are greenish grey, marked with browns, and long. Incubation lasts 16–21 days and is done only by the female. Hatching is often asynchronous, and hatched young are altricial, brooded by the female but fed by both sexes. Juveniles are able to fly 3–4 weeks after hatching, and will feed with adults for about two months before leaving to join other juvenile magpies. Fledging success (usually 3–4 young per nest) is lower than the typical clutch size; this is not an unusual state of affairs in species with asynchronous hatching, as some nestlings often die of starvation. Black-billed magpies reach sexual maturity at one or two years of age. The lifespan of the species in the wild is about four to six years.
Feeding